JP2003100645A - Method for manufacturing semiconductor device - Google Patents

Abstract

(57) [Problem] To prevent generation of particles due to friction between a wafer and a holding groove. SOLUTION: In a method of manufacturing an IC including a process in which polysilicon is formed on a wafer while a plurality of wafers are supported by a boat in a processing chamber, a boat loading step in which the boat is loaded into the processing chamber. In S1, the temperature of the processing chamber is set lower (380 ° C.) than the film forming temperature (620 ° C.) in the film forming step S3, and the loading speed of the boat is set to 500 to 1000 mm / min. After the boat is loaded, the temperature of the processing chamber is raised to the film formation temperature, and then the pressure in the processing chamber is reduced. [Effect] By raising the temperature of the processing chamber under the atmospheric pressure, the frictional force due to the rubbing between the wafer and the holding groove of the boat can be reduced, so that the generation of large particles due to the rubbing can be prevented, and the polysilicon film can be formed. Process quality and reliability can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a technique for preventing particles, for example, a semiconductor wafer (hereinafter referred to as a wafer) on which an integrated circuit including a semiconductor element is formed. Semiconductor integrated circuit device (hereinafter referred to as IC
Say. ) Is effective for use in the manufacturing method.

[0002]

2. Description of the Related Art Generally, a batch type vertical hot wall type low pressure CVD apparatus (hereinafter referred to as a CVD apparatus) is used in a film forming step of forming polysilicon on a wafer in an IC manufacturing method.

A conventional CVD apparatus of this type has a process tube in which a processing chamber is formed, a heater unit installed outside the process tube to heat the processing chamber, and a plurality of sheets (for example, 100 to 200 sheets). A wafer transfer device that holds the wafers of the wafer and collectively carries the wafers into and out of the processing chamber, and a wafer transfer device that transfers the plurality of wafers to and from the boat outside the processing chamber. By loading the boat holding the wafers into the processing chamber, a plurality of wafers to be processed are collectively processed (batch processing) in the processing chamber. In the conventional polysilicon film forming process using this type of CVD apparatus, a sequence of depressurizing the processing chamber after the boat is loaded into the processing chamber (boat loading) and then increasing the temperature of the processing chamber, or Alternatively, a sequence is adopted in which the pressure reduction and the temperature rise are started at the same time.

[0004]

However, in the control method in which the depressurization and the temperature rise in the processing chamber described above are carried out after the completion of the loading of the boat, the friction between the wafer and the holding groove of the boat becomes large, so that the wafer The present inventor has revealed that there is a problem in that the polysilicon film on the back surface or the boat surface falls loosely on the surface of the underlying wafer, and many large particles of 1 μm or more are generated.

An object of the present invention is to provide a method of manufacturing a semiconductor device capable of preventing the generation of large particles due to the rubbing between the substrate and the holding groove of the boat.

[0006]

A method for manufacturing a semiconductor device according to the present invention is a method of manufacturing a semiconductor device, wherein the substrate is processed in a processing chamber while a plurality of substrates are supported by the boat. The temperature of the processing chamber is set lower than the temperature of the substrate processing at the time of loading into the processing chamber, and the speed of loading the boat into the processing chamber is 500 mm.
It is characterized by being set to not less than / min and not more than 1000 mm / min.

According to the above-mentioned means, the processing chamber temperature at the time of loading the boat is set lower than the substrate processing temperature, and the boat loading speed is set relatively high, so that the substrate and the boat are loaded. Since the frictional force caused by the friction with the holding groove can be suppressed to a small level, generation of large particles due to the friction can be prevented.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.

In the present embodiment, the method of manufacturing a semiconductor device according to the present invention comprises a polysilicon film forming step I
It is configured as a C connecting device, and the polysilicon film forming process is carried out by using the CVD device (batch type vertical hot wall type CVD device) shown in FIGS. 1 and 2.

As shown in FIGS. 1 and 2, C
The VD device 1 is provided with a process tube 11 integrally formed in a cylindrical shape with a lower end opened by using quartz glass. The process tube 11 is vertically arranged so that its center line is vertical, and the case (one Only the parts are shown.) 2
Supported by. A hollow portion of the process tube 11 forms a processing chamber 12 into which a plurality of wafers held in a concentric arrangement by a boat is loaded, and a lower end opening of the process tube 11 is a wafer to be processed. A furnace port 13 for taking in and out is constructed. Therefore, the inner diameter of the process tube 11 is set to be larger than the maximum outer diameter of the wafer to be handled.

The lower end surface of the process tube 11 is in contact with the upper end surface of the manifold 14 with the seal ring 15 sandwiched therebetween, and the manifold 14 is supported by the housing 2 so that the process tube 11 is supported vertically. It is in a state. An exhaust pipe 16 is connected to a part of a sidewall of the manifold 14 so as to communicate with the processing chamber 12, and the other end of the exhaust pipe 16 is a vacuum exhaust device for exhausting the processing chamber 12 to a predetermined vacuum degree. (Not shown). A gas introducing pipe 17 is connected to the other part of the side wall of the manifold 14 so as to communicate with the processing chamber 12, and the other end of the gas introducing pipe 17 is a gas for supplying a gas such as a raw material gas or a nitrogen gas. It is connected to a supply device (not shown).

A heater unit 18 is concentrically provided outside the process tube 11 so as to surround the process tube 11. The heater unit 18 is supported by the housing 2 and is vertically installed. ing. The heater unit 18 is configured to heat the entire inside of the processing chamber 12 to a uniform or predetermined temperature distribution.

A seal cap 19 formed in a disk shape substantially equal to the outer diameter of the process tube 11 is concentrically arranged immediately below the process tube 11, and the seal cap 19 is an elevator 20 constituted by a feed screw mechanism. It is designed to be lifted and lowered vertically. The seal cap 19 vertically stands on the center line to support the boat 21.

The boat 21 has a pair of end plates 22 and 23 arranged vertically.
And a plurality of (three in the present embodiment) holding members 24 that are vertically installed by being installed between both end plates 22 and 23. The holding member 24 is made of quartz and has a round bar shape. The holding member 24 has a plurality of holding grooves 25.
Are arranged at equal intervals in the longitudinal direction, and each holding member 24 is engraved so as to open in the same plane. Then, the outer peripheral portion of the wafer W is positioned in the same plane between the plurality of holding members 24 and each holding groove 25 is formed.
The wafer W can be held horizontally by being inserted into the holding groove 2.
The plurality of wafers W held on the boat 5 are
By means of 1, they are held horizontally and aligned with each other.

A heat insulating cap portion 26 is formed below the lower end plate 23 of the boat 21, and a disk shape having a diameter slightly larger than the outer diameter of the heat insulating cap portion 26 is formed on the lower surface of the heat insulating cap portion 26. The base 27 formed in the above is horizontally provided. In the boat 21, the base 27 is brought into contact with the upper surface of the seal cap 19 and is detachably fixed,
It is installed on the base 27.

Next, I by the CVD apparatus having the above-mentioned structure
The polysilicon film forming step of the manufacturing method of C will be described with reference to FIG.

Here, FIG. 3A shows a time chart of each step of the polysilicon film forming process, and FIG.
Shows the temperature sequence of the processing chamber, and (c) also shows the pressure sequence. In FIG. 3, S1 is a boat loading step, S2 is a temperature raising step, S2 'is a depressurizing step, S3 is a film forming step, S4 is a purging step, and S5 is a boat unloading step.

Before the boat loading step S1 shown in FIG. 3A is performed, the wafer W on which the polysilicon film is to be formed is sealed with the seal cap 1 as shown in FIG.
The boat 21 supported by 9 is loaded by the wafer transfer device (not shown).

When a plurality of wafers W designated in advance are loaded into the boat 21, as shown in FIG. 2, in the boat loading step S1 of FIG.
Is raised by the elevator 20 and carried into the processing chamber 12 of the process tube 11 (boat loading). The ascending speed of the boat 21 in the boat loading step S1 is set to 500 mm / min or more and 1000 mm or less, which is higher than the conventional boat ascending speed (about 100 mm / min). When the boat 21 reaches the upper limit, the outer peripheral portion of the upper surface of the seal cap 19 is seated on the lower surface of the manifold 14 with the seal ring 15 interposed therebetween, and the lower end opening of the manifold 14 is closed in a sealed state. 12 is in a hermetically closed state.

During this boat loading step S1, FIG.
As shown in (b), the temperature of the processing chamber 12 is kept constant at 380 ° C., which is lower than the temperature of the processing chamber 12 in the film forming step S3. Also, FIG.
As shown in (c), the pressure in the processing chamber 12 is constantly maintained at atmospheric pressure (about 1013 hPa).

As shown in FIG. 3A, in the temperature raising step S2 after the boat loading step S1 is completed, as shown in FIG.
Temperature from 380 ° C. to the processing temperature of the film forming step S3 (for example, 620 ° C.), a constant heating rate (for example, 5 ° C.
Every minute). The temperature after reaching the film formation processing temperature in the processing chamber 12 is maintained constant.

Further, as shown in FIG. 3 (c),
Even during the temperature raising step S2, the pressure in the processing chamber 12 is maintained at atmospheric pressure. Then, after the temperature of the processing chamber 12 reaches a predetermined film forming processing temperature, the depressurizing step S2 ′ is performed.
In, the pressure in the processing chamber 12 is reduced to the processing pressure (for example, 30 Pa) in the film forming step S3 by being exhausted by the exhaust pipe 16, and is maintained constant when the predetermined pressure is reached.

As shown in FIG. 3, in the film forming step S3, a source gas (for example, SiH) for forming a polysilicon film is formed with the temperature and pressure of the processing chamber 12 maintained constant. ₄ ) is supplied from the gas introduction pipe 17. Under this processing condition, a polysilicon film is formed on the wafer W in the processing chamber 12 by the thermal CVD reaction.

When the processing time preset for the film forming step S3 has elapsed, in the purging step S4,
By supplying an inert gas such as nitrogen gas to the processing chamber 12 from the gas introduction pipe 17, the processing chamber 12 is purged with nitrogen gas. By this nitrogen gas purge, the processing chamber 12
Is increased to atmospheric pressure, as shown in FIG. 3 (c).

As shown in FIG. 3B, in the purging step S4, the temperature of the processing chamber 12 is from the film forming processing temperature to the predetermined temperature designated in the boat unloading step S5 (for example, 620 ° C.). To 350 ° C.), a temperature lowering rate faster than the temperature raising step S2 (for example, 10 ° C. per minute)
To descend.

When the temperature of the processing chamber 12 falls to a predetermined temperature, the seal cap 19 holding the boat 21 is lowered by the elevator 20 as shown in FIG. 21 is unloaded from the processing chamber 12 of the process tube 11 (boat unloading). At this time, the processing chamber 1
The temperature of No. 2 is maintained constant as shown in FIG. 3 (b), and the pressure of the processing chamber 12 is maintained at atmospheric pressure as shown in FIG. 3 (c).

Thereafter, the above-described steps are repeated and the wafers W are batch processed by the CVD apparatus 1.

By the way, in the conventional film forming process in which the pressure reduction and temperature increase in the processing chamber are carried out after the boat loading step is completed, since the friction between the wafer and the holding groove of the boat becomes large, the back surface of the wafer or the surface of the boat is increased. Film of polysilicon drops onto the surface of the underlying wafer,
The present inventors have clarified that a large number of large particles of 1 μm or more are generated. This phenomenon is considered to be caused by the following principle.

As shown in FIG. 4A, there is friction between the contact surface between the wafer W and the holding groove 25, and moreover, between the silicon of the wafer W and the quartz glass of the holding groove 25. The frictional force f of is extremely large. The frictional force f increases as the pressure in the processing chamber 12 decreases. On the other hand, when the temperature of the wafer W rises, thermal expansion occurs, causing rubbing between the contact surfaces of the wafer W and the holding groove 25. That is, when the processing chamber 12 is depressurized or heated while being depressurized after the boat loading step, the wafer W and the holding groove 25 rub against each other with an extremely large frictional force f, so that large particles 31 are generated. . Then, the generated large particles 31 drop and adhere to the upper surface of the lower wafer W as shown in FIG. 4C.

When rubbing occurs between the wafer W and the holding groove 25 with a large frictional force f, as shown in FIG. A scratch 32 is generated.

Therefore, as described above, the boat 21 is raised at a high speed in the boat loading step S1 and the temperature of the processing chamber 12 is raised under the atmospheric pressure after the boat loading step S1 is completed. Large particle deposition and wafer scuffing could be reduced as shown in FIG. For example, the number of large particles 31 having a size of 1 μm or more is reduced to 10 or less per wafer, whereas the conventional number is 20 to 30 per wafer. This is considered to be due to the following reasons.

By raising the temperature of the processing chamber 12 under atmospheric pressure, the frictional force f acting between the contact surfaces of the wafer W and the holding groove 25 can be suppressed to a small level, so that the temperature of the wafer W rises. Due to the thermal expansion, the generation of the large particles 31 can be prevented even if rubbing occurs between the contact surfaces of the wafer W and the holding groove 25.

In the process in which the boat 21 is carried into the processing chamber 12, the wafer W is heated by the preheating temperature (for example, 380 ° C.) of the processing chamber 12, but this heating is uncontrolled heating. The thermal expansion of the wafer W due to is irregular. In the present embodiment, the boat 21 is loaded into the processing chamber 12 at a high speed, so that the in-plane temperature difference Δt (° C.) of the wafer W can be suppressed to a small level, and the wafer W is not heated due to this heating. Regular thermal expansion can be suppressed small. That is, the thermal expansion of the wafer W is limited to that caused by the controlled heating in the temperature raising step S2 after the boat loading step S1 is completed. Therefore, the frictional force f acting between the wafer W and the holding groove 25 is desired. Therefore, the large particles 31 can be prevented from being generated.
Moreover, by raising the boat 21 at a high speed,
Since the period of the temperature raising step S2 can be relatively extended by shortening the period of the boat loading step S1, the frictional force f acting between the wafer W and the holding groove 25 can be further increased by controlling the thermal expansion of the wafer W. It can be controlled more precisely.

As described above, according to the present embodiment, it is possible to prevent the generation of large particles and scratches on the wafer surface, so that the quality and reliability of the polysilicon film forming process can be improved. As a result, it is possible to prevent the yield of the IC manufacturing method from decreasing.

Needless to say, the present invention is not limited to the above-mentioned embodiment, and various modifications can be made without departing from the scope of the invention.

For example, according to the above consideration, the higher the boat ascending speed is, the better. However, from the viewpoint of the inertial force applied to the boat and the wafer, the boat elevator capacity, etc., the boat ascending speed is 1000 mm / It is desirable to set it to less than a minute.

The temperature rise in the processing chamber in the temperature raising step is 3
The temperature is not limited to 20 ° C. to 620 ° C., and it is desirable that the temperature be appropriately set according to the processing temperature specified in the polysilicon film forming process.

Although the polysilicon film forming process has been described in the above-mentioned embodiments, it can be used for all process steps in the IC manufacturing method such as a film forming process of another film type, an oxidizing process, an annealing process and a diffusion process. You can

Further, although the case where the batch type vertical hot wall type low pressure CVD apparatus is used has been described in the above embodiment, the present invention is not limited to this, and the batch type horizontal hot wall type low pressure CVD apparatus or the batch type vertical hot type CVD apparatus is used. It can be applied to all IC manufacturing methods using a semiconductor manufacturing apparatus such as a wall type heat treatment apparatus.

[0040]

As described above, according to the present invention,
Since generation of large particles due to friction between the substrate and the holding groove of the boat can be prevented, the quality and reliability of the method for manufacturing a semiconductor device can be improved.

[Brief description of drawings]

FIG. 1 is a front cross-sectional view showing a state before a boat is loaded in a polysilicon film forming step of a method for manufacturing an IC according to an embodiment of the present invention.

FIG. 2 is a front cross-sectional view showing the state after carrying in the boat.

3A is a time chart of each step of a polysilicon film forming process, FIG. 3B is a temperature sequence of the processing chamber, and FIG. 3C is a pressure sequence of the same.

FIG. 4 is an explanatory diagram for explaining a phenomenon in which scratches and particles are generated.

FIG. 5 is an explanatory diagram for explaining the effect of preventing scratches and particles.

[Explanation of symbols]

W ... Wafer (substrate), 1 ... CVD apparatus, 2 ... Housing, 11
... process tube, 12 ... processing chamber, 13 ... furnace opening, 14
… Manifold, 15… Seal ring, 16… Exhaust pipe,
17 ... Gas introduction pipe, 18 ... Heater unit, 19 ... Seal cap, 20 ... Elevator, 21 ... Boat, 22 ...
Upper end plate, 23 ... Lower end plate, 24 ... Holding member, 25 ... Holding groove, 26 ... Insulating cap portion, 27 ... Base, 31 ... Large particle, 32 ... Scratch, S1
… Boat loading step, S2… Raising temperature step, S2 ′…
Decompression step, S3 ... Film formation step, S4 ... Purge step, S5 ... Boat unloading step.

Continued front page    F-term (reference) 4K030 BA29 BB03 CA04 FA10 GA13                       HA15 JA09 JA10 JA12 LA15                 4M104 BB01 DD43 DD44 DD45 HH20                 5F045 AA06 AB03 AC01 AD10 AE19                       BB15 DP19 EC02 EK06 EK28                       EN04 GB05

Claims (2)

[Claims] 1. A process in which a plurality of substrates are supported by a boat in a processing chamber and the substrate is processed, the temperature of the processing chamber is set to the substrate when the boat is loaded into the processing chamber. The temperature is set lower than the processing temperature, and the speed of loading this boat into the processing chamber is 500 mm.
/ Min or more and 1000 mm / min or less, The manufacturing method of the semiconductor device characterized by the above-mentioned. 2. The temperature of the processing chamber is raised to the temperature of the processing after the boat is loaded into the processing chamber, and then the pressure of the processing chamber is set to the pressure when the boat is loaded into the processing chamber. The method of manufacturing a semiconductor device according to claim 1, wherein the pressure is reduced to a lower processing pressure.